The Washington Nationals won Monday’s game against the Detroit Tigers 5-4 on Clint Robinson’s walk-off home run, but it was superstar Bryce Harper‘s actions during the ensuing celebration that turned heads.

MLB.com provided a video that seemed to show Harper cursing at an umpire as the Nationals mobbed Robinson:

Bill Baer of NBC Sports noted Harper “had apparently been chirping” at home plate umpire Brian Knight since he was called out on strikes in the bottom of the fourth inning. After Danny Espinosa struck out looking in the ninth, Knight ejected Harper from the dugout, per Baer.

Robinson then hit the game-winning homer in the next at-bat (the umpires reviewed the play to make sure a fan didn’t interfere with the ball), prompting the celebration.

Ken Rosenthal of Fox Sports reported Harper is facing a fine or suspension because ejected players are not allowed to return to the field.

Harper made headlines in March in a story that appeared in ESPN The Magazine (via Eddie Matz of ESPN.com) when he said, “Baseball’s tired. It’s a tired sport because you can’t express yourself. You can’t do what people in other sports do.”

Harper—who was seen sporting a hat that said “Make Baseball Fun Again” after those early-season quotes—certainly expressed himself Monday.

Harper was asked after the game if he thinks he will be fined for those expressions and said, per Chelsea Janes of the Washington Post, “If I do, I do. I’ll pay it. Maybe he’ll get fined too.” 

He also explained his mindset, per Baseball Tonight: “I was pretty upset…I let him hear what I had to say, let him hear it again and you know, so what?”

Following Monday’s game, Harper is hitting .260 with 10 home runs and 27 RBI in the 2016 campaign. That would mark the lowest batting average of his career, if it holds up, but he is also boasting an impressive .434 on-base percentage and 1.054 OPS on the season, per ESPN.com.

His on-base percentage is so high because opposing pitching staffs have treated him with such caution. The Chicago Cubs walked him six times and hit him with a pitch Sunday, which marked the first time a player reached base safely seven times without an official at-bat in one game in 100 years, per ESPN Stats & Info (via Jayson Stark of ESPN).

Harper won the 2015 National League MVP with a .330 batting average, 42 home runs, 99 RBI and a 1.109 OPS.

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